Please I need help. I have made an transaction online using bitcoin, but the order cancelled and now my bitcoins are stuck. I've been using coinb.in the first time a while ago and was able to do it successfully. Now the private key is not letting me pass the same one I used last time. What can I do to get back my bitcoins?
You will need to know if the transaction is confirmed or not, if not confirmed, I do not know if you can double spend or cancel the unconfirmed bitcoin using coinb.in, but you can import your seed phrase on electrum to be able to cancel or double spend the transaction, provided if the transaction support replace-by-fee.
If the transaction support replace-by-fee, either you cancel the transaction with high fee, or pump the fee with a higher fee, and see if truly the order is cancelled, but sending message to their customer care will be the next option, in which their support will be able to help you when the transaction is confirmed but maybe the order is still cancelled. But cancelling the transaction if not confirmed yet with high fee will send back the funds back into your wallet.
If you are really confused about the state of your transaction, you can check blockchain explorer (like blockchair.com) to see if the transaction supports replace-by-fee and also if still stuck or confirmed.
If it does not support replace-by-fee, I will advice you to just wait until it is confirmed. You can use
https://www.viabtc.com/tools/txaccelerator free acceleratator to accelerate the transaction if the fee used is not less than 10 sat/byte. You can paste the txid on this
thread for help.
If the order is canceled and the transaction is confirmed, you need to contact the merchant to refund you. Coinb.in can't help because you won't have access to the private key that belongs to the recipient.
OP says the transaction is stuck, which probably means the transaction is not confirmed yet, also the reason that would result to the cancellation of an order placed.